Answer to Question #174260 in Python for Paul Carpenter

Question

Modify your program from Learning Journal Unit 7 to read dictionary items from a file and write the inverted dictionary to a file. You will need to decide on the following:

• How to format each dictionary item as a text string in the input file.
• How to covert each input string into a dictionary item.
• How to format each item of your inverted dictionary as a text string in the output file.

Create an input file with your original three-or-more items and add at least three new items, for a total of at least six items.

Include the following in your Learning Journal submission: 

• The input file for your original dictionary (with at least six items).
• The Python program to read from a file, invert the dictionary, and write to a different file.
• The output file for your inverted dictionary.
• A description of how you chose to encode the original dictionary and the inverted dictionary in text files.

Answer 1

# read a file containing a dictionary and returns a dictionary
def read_dictionary(filename):
    dictionary={}
    with open(filename,'r') as infile:
        for line in infile.readlines():
            line = line.strip().split(':')
            key = line[0].strip('\'')
            values = [item.strip('\'') for item in line[1].strip('[]').split(',')]
            dictionary[key]=values
    return dictionary

# inverts the dictionary and returns the reversed dictionary
def invert_dict(d):
    inverse={}
    for key, items in d.items():
        for item in items:
            inverse[item]=key
    return inverse

# takes in a dictionary and the filename and writes the dictionary to that file
def write_to_file(inverted_dictionary,filename):
    with open(filename,'w') as outfile:
        for key,value in inverted_dictionary.items():
            outfile.write('\'{0}\':[\'{1}\']\n'.format(key,value))
    print('{} updated successfully.'.format(filename))



def main():
    infile_name = 'dictionary.txt' # file that needs to be read from 
    d = read_dictionary(infile_name) # reads the file which returns a dictionary
    reversed_d = invert_dict(d) # reverses the dictionary and return the reversed dictionary
    print(reversed_d) # you can comment this line
    outfile_name='inverted_dict.txt' # file that needs to be updated with the reversed dictionary
    write_to_file(reversed_d,outfile_name) # writes dictionary to the file


main()